1. Field of the Invention
The present invention relates to an air conditioner, for use in a vehicle, that blows conditioned air to a plurality of spaces in a vehicle cabin, and more particularly relates to air conditioning control conducted when only one passenger is seated in the vehicle cabin.
2. Description of the Related Art
For example, as disclosed in Japanese Unexamined Patent Publication (Kokai) No. 57-167819, an air conditioner for use in a vehicle is conventionally known in which the temperature in a space on the driver's seat side and that in a space on the passenger seat side are independently controlled in accordance with the set temperature of a temperature set device on the driver's seat side and that of a temperature setting device on the passenger seat side.
According to the conventional technique described above, even when only a driver is seated in a vehicle cabin, the temperature in a space on the passenger seat side is controlled. Accordingly, air conditioning can be comfortably conducted for the driver. On the other hand, energy is wasted to conduct air conditioning for the space on the passenger seat side, which is referred to as a first problem, hereinafter.
According to Japanese Unexamined Utility Model Publication (Kokai) Nos. 59-186114 and 61-128114, an air conditioner for use in a vehicle is disclosed in which only a space on the driver's seat side is air-conditioned and a space on the passenger seat side and that on the rear seat's side are not air-conditioned when only a driver is seated in the vehicle cabin.
In this air conditioner, the first problem described above can be solved from the viewpoint of conducting air conditioning only in the space on the driver's seat side. On the other hand, when air conditioning is conducted in the rays of the summer sun in accordance with the inside air circulation mode, whereas the space on the passenger seat side and that on the rear seat side are not air-conditioned, the temperature rises in these spaces. As a result, the average temperature in the vehicle cabin is raised. Inside air of a high temperature is sucked into an air conditioning duct from an inside air entrance, and introduced to an upstream portion of an evaporator. As a result, the temperature of air in the upstream portion of the evaporator is raised, and a difference of enthalpy of air is increased before and after it passes through the evaporator.
When the difference of enthalpy of air before and after it passes through the evaporator is increased, the cooling load of the evaporator is increased. As a result, the power consumption of a compressor is increased, which is referred to as a second problem, hereinafter.
The first and second problems are not necessarily caused when the difference of enthalpy of air before and after it passes through the evaporator is increased. For example, in the case where a heat exchanger such as a hot water type heater, electric heater, combustion type heater and Peltier element is provided instead of the evaporator, the first and second problems are also caused when the difference of enthalpy of air before and after it passes through the heat exchanger is increased.